Treatment to eliminate polysilicon defects induced by metallic contaminants

ABSTRACT

A method and apparatus are provided for eliminating contaminants including metallic and/or hydrocarbon-containing contaminants on a surface of a semiconductor substrate by heating a semiconductor substrate which may have contaminates on the surface thereof to an elevated temperature within an integrated closed system while simultaneously purging the integrated closed system with a chlorine-containing gas. At the elevated temperatures the chlorine dissociates from the chlorine-containing gas and reacts with the contaminates on the substrate surface to form volatile chloride byproducts with such contaminants which are removed from the integrated closed system while the substrate is continuously heated and purged with the chlorine-containing gas. Subsequently, the substrate is moved to a cooling chamber within the integrated closed system and cooled to provide a semiconductor substrate having a clean surface.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to a method and apparatusfor fabricating semiconductor devices and, in particular, to a methodand apparatus for cleaning a substrate surface by, for example,eliminating polysilicon defects induced by metallic contaminants.

[0003] 2. Description of Related Art

[0004] In the production of semiconductor devices, a semiconductorsubstrate, such as a silicon substrate, may be formed comprising anumber of varying block levels or layers whereby such block levels mayinclude various structures formed over the semiconductor substrate. Forexample, block levels may include varying structures over the siliconsubstrate which define the semiconductor devices such as resistors, PFETwells and NFET wells in CMOS technology, and the like.

[0005] As will be recognized, the varying structures, or varying blocklevels, may be made by processes including photolithography, ionimplant, resist strip, wet cleaning processes, and the like. An inherentproblem of these block levels, and the processes used to define themover the silicon substrate, is that they produce contaminants including,for example, metallic contaminants and hydrocarbon-containingcontaminants over the substrate which remain thereon to contaminate thesurface. During the semiconductor manufacturing process, contaminantsincluding metallic contaminants and hydrocarbon-containing contaminantsmay be deposited on both the substrate front-side (chip side) andback-side. Front-side contaminants are typically introduced from tracemetallics in the photoresist while backside contaminants are typicallyintroduced from the semiconductor processing equipment such as, forexample, automated substrate handlers and chucks. This inventionaddresses both substrate front-side and back-side metallic removal.

[0006] As will be further recognized, if the metallic contaminants arenot removed from the substrate front-side or back-side prior to eitherthe gate oxidation or the polysilicon deposition processes, a grossdefect may be induced. It is preferable to remove the contaminants priorto gate oxidation to reduce the potential for gate oxide “pinholes”.These “pinholes” can render the device either non-functional orunreliable due to poor gate oxide integrity. Additionally, removal ofthe metallic contaminants will prevent the formation of polysilicondefects, herein referred to as “peppery polysilicon”, which can resultin shorts between polysilicon lines.

[0007] The microelectronics industry has faced problems with pepperypolysilicon since it first started using polysilicon as a gateconductor. Several techniques are aimed at controlling pepperypolysilicon including, for example, reducing the metallics within thedeposited photoresist, and improving both the dry steps and wet cleansteps used to define the various block levels. However, such prior arttechniques do not completely eliminate the metallic contaminants overthe substrate surface, and thus do not prevent the occurrence of pepperypolysilicon. Therefore, known techniques can still lead to semiconductorfailure in the field.

[0008] Prior art is also directed to controlling contaminates within thedeposition tools used for gate formation. For instance, in U.S. Pat. No.3,279,946, a process is disclosed wherein a reactor chamber, or aconventional semiconductor deposition tool, is preconditioned prior to asemiconductor material deposition. The tool is preconditioned by heatingthe reactor in the presence of a reactant gas, preferably HCl orchlorine, which reacts with donor impurities on the walls of the chamberto merely remove impurities in the reactor prior to a semiconductormaterial deposition on a clean wafer. This approach is problematic asthe chlorine eventually induces corrosion of the deposition tooling inthe reactor whereby the corrosion can actually increase metalliccontamination during the semiconductor material deposition. Since theprior art does not describe any in-situ cleaning of metal contaminantsfrom a substrate surface, or cleaning of the corroded depositiontooling, peppery polysilicon will likely result and the semiconductormay fail.

[0009] Furthermore, as semiconductor technologies, such as CMOStechnologies, continue to decrease in size, and thus require thinnertransfer gate oxides, the known cleaning and/or metallic contaminationremoval processes do not completely clean the substrate surface and/oreliminate metallic contaminants from the substrate surface. For example,the process of removing metallic contaminants from a substrate surfaceusing a chlorinated environment during gate oxidation transfer processesis used for thick gate oxide depositions. In such processes, themetallics are removed as a result of the substrate being exposed to thechlorinated environment for the extended period of time it takes todeposit the thick gate oxide. However, such techniques are not effectiveor efficient in removing metallic contaminants from substrates havingthin gate oxide. To produce the thinner gate oxide the substrate will beexposed to the chlorinated environment for a limited time since the gateoxide deposition time is reduced to produce the thinner gate oxide.Thus, metallic contaminants may remain on the thin gate oxide resultingin peppery polysicon, as well as pinholes in the thinner gate oxide,whereby gate oxide integrity may be compromised, and polysilicon shortsand semiconductor failure may occur.

[0010] Bearing in mind the problems and deficiencies of the prior art,it is therefore an object of the present invention to provide a methodand apparatus which cleans and/or removes contaminants, includingmetallic contaminants and hydrocarbon-containing contaminants, from asurface of a substrate to provide the substrate with a clean surface foruniform gate formation.

[0011] It is another object of the present invention to provide a methodand apparatus to clean and/or reduce residual metallic contamination ona surface of a semiconductor substrate after completion of all blocklevels.

[0012] A further object of the present invention is to provide a methodand apparatus to clean and/or reduce residual metallic contamination ona surface of a semiconductor substrate prior to sacrificial oxideremoval.

[0013] Another object of the present invention is to provide a methodand apparatus of preventing oxides formed on a semiconductor substratesurface prior to gate formation.

[0014] Still another object of the present invention is to provide amethod and apparatus of forming a clean surface on a semiconductorsubstrate to provide for a high quality gate oxide transfer.

[0015] It is also an object of the present invention to provide a methodand apparatus for the uniform formation of a gate oxide layer across thesurface of a semiconductor substrate.

[0016] Still other objects and advantages of the invention will in partbe obvious and will in part be apparent from the specification.

SUMMARY OF THE INVENTION

[0017] The above and other objects and advantages, which will beapparent to one of skill in the art, are achieved in the presentinvention which is directed to, in a first aspect, a method ofeliminating metal contaminants on a surface of a semiconductorsubstrate. The method comprises the steps of providing a semiconductorsubstrate which may have metallic contaminants and/orhydrocarbon-containing contaminants on a surface thereof into amainframe. The pressure and atmosphere of the mainframe is thenevacuated to an oxygen-free environment at a pressure of less than about1 Torr. Subsequently, the semiconductor substrate is heated to anelevated temperature, preferably to a temperature ranging from about500° C. to about 700° C. for a time ranging from about 5 minutes toabout 30 minutes, within the mainframe. While heating the substrate, thesubstrate is simultaneously purged and a surface thereof contacted witha chlorine-containing gas, preferably HCl or Cl₂ by a chemical vapordeposition process, which may form volatile metallic byproducts withmetallic contaminants and/or volatile byproducts with thehydrocarbon-containing contaminants thereover the substrate surface.During the heating and purging of the semiconductor substrate in themainframe, the surface of the substrate is cleaned and/or volatilebyproducts may be removed from the surface of the semiconductorsubstrate to provide a semiconductor substrate having a clean surface.

[0018] In the preferred embodiment, the substrate to be cleaned whichmay have metallic contaminants and/or hydrocarbon-containingcontaminants on a surface thereof preferably comprises a siliconsubstrate with a plurality of block levels thereover which maycontaminate the surface of the substrate by providing thereover metalliccontaminants comprising metals including transition metals,inner-transition metals, and metalloids, and/or hydrocarbon-containingcontaminants. Alternatively, a plurality of semiconductor substrates tobe cleaned and/or which may have the contaminants on surfaces thereofmay be provided into the mainframe whereby the substrates are retainedby a workpiece during the heating, purging and cleaning process ofremoving metallic and/or hydrocarbon-containing contaminants from thesurfaces of the substrates within the mainframe.

[0019] In the preferred embodiment, the apparatus for cleaning and/oreliminating metallic and/or hydrocarbon-containing contaminants on asurface of a semiconductor substrate comprises a mainframe having atleast one workpiece holder adapted to hold a semiconductor substratewhich may have metallic and/or hydrocarbon-containing contaminants on asurface thereof, at least one heating element adapted to heat themainframe to an elevated temperature, at least one input line adapted toprovide the chlorine-containing vapor into the mainframe, at least oneoutput line adapted to remove the volatile byproducts from themainframe, and at least one cooling chamber adapted to cool thesemiconductor substrate having the clean surface. More preferably, theheating chamber comprises the at least one component for heating thesemiconductor substrate to the elevated temperature, the at least onecomponent for providing the chlorine-containing gas over and contactingthe surface of the substrate to form the volatile byproducts with themetallic and/or hydrocarbon-containing contaminants, and the at leastone component for removing the volatile byproducts from the closedheating chamber within the closed mainframe.

[0020] More preferably, the semiconductor substrate is adapted to becontinuously heated in the mainframe wherein the mainframe is a closedmainframe comprising at least the heating chamber and the coolingchamber directly in contact with each other. The heating chamber of themainframe may comprise a closed heating chamber whereby a door seals theheating chamber from at least one other chamber within the mainframe,preferably from the cooling chamber. In such an embodiment, themainframe further comprises a means for transferring the semiconductorsubstrates directly from the cooling chamber to the heating chamber andvice versa. Preferably the means for transferring the semiconductorsubstrates from one chamber to the other is the at least one workpieceholder adapted to hold a semiconductor substrate which may have metallicand/or hydrocarbon-containing contaminants on a surface thereofcomprising a pedestal whereby the substrates are provided over andsecured to the pedestal.

[0021] Once the substrates to be cleaned and/or which may have metallicand/or hydrocarbon-containing contaminants on surfaces thereof areprovided within the mainframe, the pressure and atmosphere of themainframe are then evacuated to an oxygen-free environment preferably toa pressure ranging from about 50 mTorr to about 400 mTorr. In thepreferred embodiment, the substrates are provided over the pedestalwhereby the pedestal transfers the substrates from the cooling chamberto the heating chamber within the closed mainframe. The door then sealsthe heating chamber to provide the closed heating chamber whereby thesemiconductor substrate is then adapted to be continuously heated in theheating chamber to the elevated temperature.

[0022] In the present invention, the chlorine-containing gas, at theelevated temperature, is adapted to clean the substrate surface and/orform the volatile metallic byproducts whereby chlorine dissociates fromthe chlorine-containing gas to react with the metallic contaminantsthereby forming the volatile byproducts which may be removed from thesurface of the substrate. Preferably, the volatile metallic and/orhydrocarbon-containing byproducts are removed from the substrate surfaceprior to providing a gate oxide layer over said substrate surface andprior to removal of a sacrificial oxide.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The features of the invention believed to be novel and theelements characteristic of the invention are set forth withparticularity in the appended claims. The figures are for illustrationpurposes only and are not drawn to scale. The invention itself, however,both as to organization and method of operation, may best be understoodby reference to the detailed description which follows taken inconjunction with the accompanying drawings in which:

[0024]FIG. 1 is a schematic diagram of a closed mainframe system of thepresent invention having a heating chamber and a cooling chamber wherebya plurality of substrates to be cleaned which may have metallic and/orhydrocarbon-containing contaminants on a surface thereof are positionedwithin the cooling chamber of the closed system.

[0025]FIG. 2 is a schematic diagram of the closed mainframe system ofFIG. 1 whereby the plurality of substrates to be cleaned which may havemetallic and/or hydrocarbon-containing contaminants on surfaces thereofhave been transferred to the heating chamber for removal of metalliccontaminants from the substrate surfaces.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0026] In describing the preferred embodiment of the present invention,reference will be made herein to FIGS. 1-2 of the drawings in which likenumerals refer to like features of the invention. Features of theinvention are not necessarily shown to scale in the drawings.

[0027] It has been found that by using a chlorine-containing gas atelevated temperatures, within an integrated closed system, cleans asubstrate surface by converting contaminants over the surface thereof toform volatile chlorides which are then removed from the system toprovide a clean substrate surface. The present invention is aimed atovercoming the problems associated with the defects caused by pepperypolysilicon due to metallic contaminants and the problems associatedwith hydrocarbon-containing contaminants over the surface of thesubstrate. For example, metallic contaminants on a substrate surface maybe converted to the volatile chloride byproducts of such metalcomponents, or alternatively hydrocarbon-containing contaminants, forexample oils and greases, on a substrate surface may be converted tocarbon chloride byproducts of such hydrocarbon-containing contaminants.In the present invention, the semiconductor substrate may becontaminated and provided within the integrated closed system to cleanthe substrate surface, or alternatively, a substrate which may becontaminated may be provided within the integrated closed system as apreventative measure for providing a clean substrate surfaces. Once thevolatile chloride byproducts of the contaminants are formed, they maythen be removed from both the surface of the substrates and the closedsystem to provide a substrate surface free of contaminants therebyproviding the substrate with a clean surface for uniform gate formation,for example, free of metallic contaminants to avoid peppery polysiliconprior to gate oxide deposition.

[0028] In the present invention, the substrate is placed within aheating chamber of the integrated closed system and heated to anelevated temperature while simultaneously contacting and purging thesubstrate surfaces which may have the contaminants with thechlorine-containing gas. During such process, the chlorine of thechlorine-containing gas dissociates from the chlorine-containing gas atthe elevated temperatures to react with contaminants on the surface ofthe substrate to form volatile chlorides. For example, the dissociatedchlorine may react with the metallic contaminants on a surface of thesubstrate to form volatile metallic chlorides which are then pumped outof the furnace while the closed system continuously heats and purges thesubstrate with the chlorine-containing gas. Subsequently, the cleanedsubstrate is moved to a cooling chamber within the integrated closedsystem and cooled for subsequent substrate finishing procedures.

[0029] In the preferred embodiment, the present method of continuouslyheating, purging and cleaning the substrate surface with thechlorine-containing gas to clean and/or remove the formed volatilechloride byproducts to provide a clean substrate surface is preferablyperformed after the substrate has received all block levels but prior toreceiving the gate oxidation process. Using the method and apparatus ofthe present invention, while within the continuous and uninterruptedclosed system, a semiconductor substrate surface, such as a siliconsubstrate surface, is cleaned of contaminants without effecting oretching the underlying silicon substrate. This permits the formation ofa uniform gate layer, such as a gate oxide layer, across the surface ofthe substrate.

[0030] Further, by integrating the heating, purging and formation of thevolatile chloride byproduct processes under a constant furnace, andsubsequently cooling the substrate within the integrated closed system,the cleaned substrate is not exposed to air, or oxygen, during suchsteps. Integrating these steps in a continuous closed system preventsexposing the cleaned substrate surface to air and greatly reduces theprobability that oxygen will react with contaminants to form oxides overthe surface of the substrate. In cleaning or eliminating thecontaminants from the substrate surface, eliminating the exposure of thesubstrate to oxygen during cleaning of the substrate results in a moreuniform formation of a subsequent gate oxide layer, without additional,and at times ineffective, substrate cleaning steps. As used herein, theterms “clean”, “cleaned”, “pre-clean” and “cleaning” each refer to theremoval of the contaminants or other impurities from a surface of asemiconductor substrate. Subsequently, uniform gate oxide andpolysilicon layers may be formed over the cleaned substrate surface,whereby additional substrate cleaning steps are not required to removeremaining contaminants.

[0031] As illustrated in FIG. 1, an integrated, continuous closedsystem, is preferably used to heat, purge, and clean a surface ofsubstrate 10 by, for example, removing contaminants including metalliccontaminants and hydrocarbon contaminants from the surface thereof andsubsequently cool the substrate 10 whereby each step is performed withinthe integrated, oxygen-free closed system. The preferred integratedclosed system of the present invention comprises a mainframe 50 whichmay have one or more chambers, such as 60 and 70, integrated withinmainframe 50. Preferably, the mainframe 50 of the integrated closedsystem comprises at least one heating chamber 60 and at least onecooling chamber 70 as separated by the dashed line of reference numeral52. The substrate 10 is heated, purged, and volatile chloride byproductsremoved within the heating chamber 60, and the substrate is then cooled,or allowed to equilibrate to ambient temperature, in the cooling chamber70. Furthermore, the mainframe 50 may also include a mechanism totransfer a workpiece having a plurality of substrates 10 betweenchambers without interrupting the integrated closed system, as well as aplurality of input and output lines for introducing and removing gasesfrom the mainframe 50, respectively.

[0032] In the preferred embodiment, the integrated closed system havingmainframe 50 preferably comprises a furnace such as, for example, a LowPressure Chemical Vapor Deposition furnace, a Rapid Thermal ChemicalVapor Deposition (RTCVD) single wafer process chamber. As it will berecognized by one skilled in the art, similar process conditions asthose defined in the present invention may be used when employing aRTCVD process. As illustrated in FIG. 1, a plurality of semiconductorsubstrates or wafers 10 which may have contaminants including metalliccontaminants and hydrocarbon contaminants on surfaces thereof, oralternatively may not have contaminants on a surface thereof, areprovided within mainframe 50. The plurality of semiconductor substrates10 are provided within a means for holding the substrates, such as, aboat, or workpiece 14 within the mainframe 50. The workpiece 14 havingthe substrates 10 is provided over the mechanism to transfer theworkpiece, or substrates 10, between chambers without interrupting theintegrated closed system. In the preferred embodiment, the mechanism totransfer the workpiece 14 within the mainframe 50 comprises a pedestal16 provided over a door 18. The pedestal 16 holds workpiece 14 inposition while door 18 moves the workpiece from one chamber to anotherwithin the mainframe 50. Door 18 is further adapted to seal workpiece 14having the substrates 10 within the heating chamber of the integratedclosed system.

[0033] As shown in FIG. 1, the workpiece 14 holds the plurality ofsemiconductor substrates 10 over the pedestal 16 and door 18 whereby theworkpiece 14 having the substrates 10 is first provided within thecooling chamber 70 of the mainframe 50. Subsequently, the workpiece 14having substrates 10 is transferred to the heating chamber 60, asillustrated in FIG. 2, whereby the substrates are heated, contacted andpurged with the chlorine-containing gas, and the gaseous chloridebyproducts removed. Next, the container 14 having the substrates 10 istransferred from the heating chamber 60 to the cooling chamber 70 withinmainframe 50 for cooling.

[0034] In the present invention of cleaning the substrate and/oreliminating contaminants from the surface thereof, including metalliccontaminants and hydrocarbon contaminants, the substrate 10 may comprisea silicon substrate comprising a plurality of varying block levels. Suchblock levels may include processes that define various substrates suchas resistors, PFET wells and NFET wells in CMOS technology, and thelike. In defining the various substrates, the plurality of varying blocklevels may comprise processes including photolithography, ion implant,resist strip, wet cleaning processes, and the like. Preferably, allblock levels have been completed on the plurality of substrates 10. Aswill be recognized, such processes may produce contaminants includingmetallic contaminants and hydrocarbon contaminants over both front andback surfaces of the substrate remaining thereon to contaminate thesurface. In contaminating the surface of the substrate with metalliccontaminants, the metal contaminants are typically introduced as tracemetallic contaminants in a photoresist over portions of the substratewhich may define the gate. As will be further recognized, these tracemetallic contaminants may comprise any transition metal,inner-transition metal, or metalloid as used in the art of the varyingblock level process. Such metals include, but are not limited to,aluminum, chromium, iron, and the like.

[0035] In the present invention, the plurality of substrates 10, whichmay have contaminants over a surface thereof, are provided over thepedestal 16 (typically made of stainless steel) whereby the pedestal isdisposed on the door 18 (typically made of stainless steel). Thesubstrates 10, which may have contaminants over a surface thereof, arethen introduced into mainframe 50, more preferably into cooling chamber70, whereby mainframe 50 is subsequently closed to provide theintegrated closed system of mainframe 50. Subsequently, mainframe 50,and each of the chambers integral thereto, will be evacuated to atypical pressure and environment such as nitrogen environment preferablyat a pressure under 1 Torr, even more preferably in the range of about50 mTorr to about 400 mTorr.

[0036] After the substrates 10 which may have contaminants over asurface thereof, including metallic contaminants and hydrocarboncontaminants, have been provided within the cooling chamber 70 of theintegrated closed system, and such system has been evacuated, thesubstrates 10 will then be transferred to the heating chamber 60 withoutbreaking the continuous closed system of mainframe 50 by anyconventional process or mechanism, preferably by the transferring meansof door 18. Preferably, the heating chamber 60 is a furnace comprising atube 62. The heating chamber 60 or furnace may also include conventionalheating elements 64 for providing heat to the furnace, at least oneinput line 66 for providing a chlorine-containing gas to the heatingchamber, and at least one output line 68 for removing the volatilechloride byproducts formed.

[0037] Once substrates 10 which may have contaminants over a surfacethereof are placed within the heating chamber 60 door 18 seals theheating chamber 60 to provide the closed, sealed heating chamber 60within the integral closed system of mainframe 50. Subsequently, theheating chamber 60 is heated by heating elements 64 to an elevatedtemperature while simultaneously the substrates, including surfacesthereof, are contacted by and purged with the chlorine-containing gasfrom the at least one input line 66. Heating elements 64 heat thechamber to an elevated temperature ranging from about 500° C. to about700° C. for a time ranging from about 5 minutes to about 30 minutes, oralternatively for a period of time at which all of contaminants over thesubstrate surface have been removed. While simultaneously heating, theheating chamber 60 is provided with the chlorine-containing gas fromline 66 at a substantially constant pressure under 1 Torr, butpreferably in the range of about 50 m Torr to about 400 mTorr. Thechlorine containing gas may comprise HCl, Cl₂, and the like. In heatingthe chlorine-containing gas to such elevated temperatures, the chlorinemolecules spontaneously dissociate from the chlorine-containing gas toform volatile, gaseous chloride byproducts with the contaminants overthe surface of the substrates 10 within the closed heating chamber ofclosed mainframe 50. At least one output line 68 of the heating chamberremoves the volatile chloride byproducts from the heating chamber whilethe substrate is being heated and purged with the chlorine-containinggas. Preferably,

[0038] In the present invention, in heating the heating chamber 60, thetemperature of substrates 10 is preferably maintained at about 500° C.to 700° C. during the contamination elimination process which cleans thesubstrate surface.

[0039] In the preferred embodiment, the heating chamber havingsubstrates 10 which may have the contaminates on a surface thereof isheat to a temperature of about 625° C. for about 20 minutes while thechamber and substrate are purged with the chlorine-containing gascomprising a chlorine gas. In heating the chlorine gas to temperaturesranging from about 500° C. to about 700° C. for about 20 minutes, thechlorine molecules spontaneously dissociate from the hydrogen in thechlorine gas to form the volatile, gaseous byproducts with thecontaminants on the surface of the substrates 10 within the closedheating chamber of closed mainframe 50. For example, wherein thesubstrates 10, within heating chamber 60, which may have metallicsurface contaminates comprising aluminum, chromium, and iron, is heatedto about 625° C. for about 20 minutes, and the chlorine is heated tosuch temperatures, the chlorine dissociates from the hydrogen to reactwith the aluminum, chromium, and iron to form volatile, gaseous metallicbyproducts comprising Al_(x)Cl_(y), Cr_(x)Cl_(y), and Fe_(x)Cl_(y).During such process, the volatile, gaseous metallic byproductscomprising Al_(x)Cl_(y), Cr_(x)Cl_(y), and Fe_(x)Cl_(y) are removed bythe at least one output line 68 within heating chamber 60 to provide aclean substrate 10 for subsequent finishing processes, such as forformation of a “pinhole” free gate oxide and subsequent defect-free, orpeppery polysilicon-free, polysilicon film. In the present invention,the volatile, gaseous metallic byproducts may be evacuated by aconventional evacuation or exhaust line with heating chamber 60 orfurnace at a constant pressure under 1 Torr, more preferably in therange of about 50 mTorr to about 400 mTorr. Alternatively, wherein thecontaminants on the surface of the substrate include hydrocarboncontaminants, the chlorine dissociates from the hydrogen to react withthe hydrocarbon to form volatile carbon chlorides which are then removedfrom the mainframe.

[0040] After cleaning and/or eliminating or removing any contaminantsfrom the surface of substrates 10, substrates 10 may then be transferredto the cooling chamber 70 of the mainframe 50. Once the substrates 10are positioned in the cooling chamber 70 the substrates may then becooled. As illustrated in FIG. 1, the cooling chamber further comprisesat least one input line 76 for providing a oxygen-free gas, such asnitrogen, helium, and the like, to the cooling chamber to cool the cleansurfaced substrates 10. In the preferred embodiment, a N₂ coolingprocess cools the clean substrates relatively free from oxygen toprevent formation of oxides on the surface of the substrate.

[0041] In the present invention, the steps within the integral closedsystem of simultaneously heating the substrate which may have metalliccontaminants over the surface thereof, purging the substrate with thechlorine-containing gas, and removing formed volatile metallic chloridebyproducts within the heating chamber and subsequently cooling thesubstrates within the cooling chamber are preferably performed prior tothe removal of the sacrificial oxide, over which all of the block levelprocessing was performed, and prior to formation of the gate oxide.

[0042] While the present invention has been particularly described, inconjunction with a specific preferred embodiment, it is evident thatmany alternatives, modifications and variations will be apparent tothose skilled in the art in light of the foregoing description. It istherefore contemplated that the appended claims will embrace any suchalternatives, modifications and variations as falling within the truescope and spirit of the present invention.

Thus, having described the invention, what is claimed is:
 1. A method ofcleaning a semiconductor substrate comprising: providing a mainframe;providing a semiconductor substrate into said mainframe; heating saidsemiconductor substrate to an elevated temperature within saidmainframe; while heating said semiconductor substrate, purging saidsemiconductor substrate with a chlorine-containing gas to form volatilechlorides within said mainframe; and removing said volatile chloridesfrom said semiconductor substrate in said mainframe to provide saidsemiconductor substrate with a clean substrate surface.
 2. The method ofclaim 1 further including said semiconductor substrate havingcontaminants on a surface thereof.
 3. The method of claim 2 wherein saidcontaminants comprise metallic contaminants on said surface of saidsemiconductor substrate.
 4. The method of claim 2 wherein saidcontaminants comprise hydrocarbon-containing contaminants on saidsurface of said semiconductor substrate.
 5. A method of eliminatingcontaminants on a surface of a semiconductor substrate comprising:providing a mainframe; providing a semiconductor substrate into saidmainframe; heating said semiconductor substrate to an elevatedtemperature within said mainframe; while heating said semiconductorsubstrate, purging said mainframe and a surface of said semiconductorsubstrate by contacting a chlorine-containing gas with said surface toform volatile chloride byproducts of contaminants within said mainframe;and removing said volatile chloride byproducts from said mainframe toprovide said semiconductor substrate with a clean substrate surface. 6.The method of claim 5 wherein said substrate comprises a siliconsubstrate having a plurality of block levels.
 7. The method of claim 5wherein said step of providing said semiconductor substrate comprisesproviding a plurality of semiconductor substrates.
 8. The method ofclaim 7 wherein said plurality of semiconductor substrates are providedwithin a workpiece for heating to said elevated temperatures.
 9. Themethod of claim 5 further comprising evacuating said mainframe to aoxygen-free environment at a pressure of less than about 1 Torr.
 10. Themethod of claim 9 wherein said pressure of said mainframe comprises apressure ranging from about 50 mTorr to about 400 mTorr.
 11. The methodof claim 5 wherein said volatile chloride byproducts of saidcontaminants comprise volatile metallic byproducts of metals selectedfrom the group consisting of transition metals, inner-transition metals,and metalloids.
 12. The method of claim 5 wherein said semiconductorsubstrate is adapted to be continuously heated in said mainframe whereinsaid mainframe comprises a closed mainframe having a heating chamber,said substrate being heated, contacted and purged within said heatingchamber while removing said volatile chloride byproducts from saidheating chamber.
 13. The method of claim 12 wherein said heating chamberof said mainframe comprises a closed heating chamber whereby a doorseals said heating chamber from at least another chamber of saidmainframe.
 14. The method of claim 12 wherein said mainframe furthercomprises a cooling chamber, and said semiconductor substrate having theclean substrate surface being directly transferred from said heatingchamber to said cooling chamber by a means adapted to transfer saidsemiconductor substrate having the clean substrate surface from saidheating chamber to said cooling chamber, and cooling said cleansubstrate surface.
 15. The method of claim 14 wherein said means adaptedto transfer said semiconductor substrate from said heating chamber tosaid cooling chamber comprises a pedestal.
 16. The method of claim 5wherein said semiconductor substrate is adapted to be continuouslyheated in a heating system to said elevated temperature.
 17. The methodof claim 16 wherein said heating system comprises a Low PressureChemical Vapor Deposition furnace.
 18. The method of claim 16 whereinsaid heating system comprises a Rapid Thermal Chemical Vapor Depositionfurnace.
 19. The method of claim 16 wherein said heating systemcomprises a plurality of interior components, at least one component forheating said semiconductor substrate to said elevated temperature, atleast one component for providing said chlorine-containing gas over andcontacting said surface to form the volatile chloride byproducts of saidcontaminants, and at least one component for removing said volatilechloride byproducts.
 20. The method of claim 5 wherein saidsemiconductor substrate is heated to said elevated temperature withinsaid mainframe ranging from about 500° C. to about 700° C.
 21. Themethod of claim 5 wherein said semiconductor substrate is heated to saidelevated temperature for a time ranging from about 5 minutes to about 30minutes.
 22. The method of claim 5 wherein said chlorine-containing gasis provided over said substrate surface by a chemical vapor depositionprocess.
 23. The method of claim 5 wherein said chlorine-containing gascomprises HCl or Cl₂.
 24. The method of claim 5 wherein saidchlorine-containing gas at said elevated temperature is adapted to formsaid volatile chloride byproducts whereby chlorine dissociates from thechlorine-containing gas to react with said contaminants thereby formingsaid volatile chloride byproducts.
 25. The method of claim 5 whereinsaid volatile chloride byproducts are removed from said substratesurface prior to providing a gate oxide layer over said substratesurface.
 26. The method of claim 5 wherein said volatile chloridebyproducts are removed from said substrate surface prior to removal of asacrificial oxide.
 27. An apparatus for cleaning a semiconductorsubstrate, said apparatus comprising: a mainframe; at least oneworkpiece holder within said mainframe adapted to hold a semiconductorsubstrate; at least one heating element adapted to heat said mainframeto an elevated temperature; at least one input line adapted to provide achlorine-containing vapor into said mainframe, said chlorine-containingvapor adapted to form volatile chloride byproducts with contaminantswithin said mainframe; and at least one output line adapted to removesaid volatile chloride byproducts from said mainframe, wherein saidapparatus is adapted to clean said semiconductor substrate surface byeliminating contaminants on a surface of said semiconductor substrate.28. The apparatus of claim 27 further comprising at least one input lineadapted to provide a vapor into said mainframe for cooling saidsemiconductor substrate having said clean surface.
 29. The apparatus ofclaim 27 wherein said mainframe comprises a plurality of interiorchambers, at least one interior chamber adapted to heat, purge andremove formed volatile chloride byproducts of said contaminant from saidsubstrate, and at least one interior chamber adapted to cool saidsemiconductor substrate having said clean surface.
 30. The apparatus ofclaim 27 wherein said mainframe comprises a Low Pressure Chemical VaporDeposition furnace.
 31. The apparatus of claim 27 wherein said elevatedtemperature ranges from about 500° C. to about 700° C.
 32. The apparatusof claim 27 wherein said mainframe is adapted to be heated at saidelevated temperature for a time ranging from about 5 minutes to about 30minutes